Plug Flow Reactor Models

Yield-Based Reactor Fractional Conversion Reactor Combined Specification Model Well-Stirred Reactor Model Plug Flow Reactor Model Two Phase Chemical Equilibrium General Phase and Chemical Equilibrium... 

The effectiveness of a fluidized bed as a ehemical reactor depends to a large extent on the amount of convective and diffusive transfer between bubble gas and emulsion phase, since reaction usually occurs only when gas and solids are in contact. Often gas in the bubble cloud complex passes through the reactor in plug flow with little back mixing, while the solids are assumed to be well mixed. Actual reactor models depend greatly on kinetics and fluidization characteristics and become too complex to treat here. 

We wish to compare the performance of two reactor types plug flow versus CSTR with a substrate concentration of Csf = 60g-m 3 and a biomass yield of Y = 0.1. In a plug flow bioreactor with volume of 1 m3 and volumetric flow rate of 2.5 m -li what would be the recycle ratio for maximum qx compared with corresponding results and rate models proposed for the chemostat ... 

As with continuous processes, the heart of a batch chemical process is its reactor. Idealized reactor models were considered in Chapter 5. In an ideal-batch reactor, all fluid elements have the same residence time. There is thus an analogy between ideal-batch reactors and plug-flow reactors. There are four major factors that effect batch reactor performance ... 

The model is a reactor in plug flow with inlet flows on the side programmed to result in a particular RTD. The relation between the distribution functions is... 

A viscous liquid is to react while passing through a tubular reactor in which flow is expected to follow the convection model. What conversion can we expect in this reactor if plug flow in the reactor will give 80% conversion ... 

The various systems that are modeled by complete mix reactors and plug flow reactors are given in Table 6.1. 

EXAMPLE 6.6 Degradation in various systems modeled by one complete mixed reactor, one plug flow reactor, and several complete mixed reactors-in-series... 

Plug Flow Reactor. The plug flow reactor model requires only a residence time tf). So, the tracer cloud is used to determine tp. 

Estimate the height of the bed to achieve the same performance of the reactor by using the appropriate simplified model, assuming that the liquid phase remains saturated with 02 throughout the reactor length, plug-flow conditions exist, and the external wetting of the catalyst particle is complete. 

The main physicochemical processes in thin-film deposition are chemical reactions in the gas phase and on the film surface and heat-mass transfer processes in the reactor chamber. Laboratory deposition reactors have usually a simple geometry to reduce heat-mass transfer limitations and, hence, to simplify the study of film deposition kinetics and optimize process parameters. In this case, one can use simplified gas-dynamics reactor such as well stirred reactor (WSR), calorimetric bomb reactor (CBR, batch reactor), and plug flow reactor (PFR) models to simulate deposition kinetics and compare theoretical data with experimental results. 

Tubular Reactors. The simplest model of a tubular reactor, the plug-flow reactor at steady state is kinetically identical to a batch reactor. The time variable in the batch reactor is transformed into the distance variable by the velocity. An axial temperature gradient can be imposed on the tubular reactor as indicated by Gilles and Schuchmann (22) to obtain the same effects as a temperature program with time in a batch reactor. Even recycle with a plug flow reactor, treated by Kilkson (35) for stepwise addition without termination and condensation, could be duplicated in a batch reactor with holdback between batches. 

Gas-phase reacdotis are carried out primarily in tubular reactors where the flow is generally turbulent. By assuming that there is no dispersion and ttiere are no radial gradients in either temperature, velocity, or concentration, we can model the flow in the reactor as plug-flow. Laminar reactors are discussed in Chapter 13 and dispersion effects in Chapter 14. The differential form of the design equation... 

Another way of looking at the segregation model for a continuous-flow system is the PFR shown in Figures 13-15(a) and (b). Because the fluid flows down the reactor in plug flow, each exit stream corresponds to a specific residence time in the reactor. Batches of molecules are removed from the reactor at different locations along the reactor in such a manner so as to duplicate the RTD function, (/). The molecules removed near the entrance to the reactor... 

For flow reactors, the plug-flow and the CSTR models represent two limiting cases. The former represents continuous reactor without any mixing, where the reactant concentrations decrease along the reactor. The latter represents a reactor with complete mixing where the outlet reactant concentration exists throughout... 

In practice, the fluid velocity profile is rarely flat, and spatial gradients of concentration and temperature do exist, especially in large-diameter reactors. Hence, the plug-flow reactor model (Fig. 7.1) does not describe exactly the conditions in industrial reactors. However, it provides a convenient mathematical means to estimate the performance of some reactors. As will be discussed below, it also provides a measure of the most efficient flow reactor—one where no mixing takes place in the reactor. The plug-flow model adequately describes the reactor operation when one of the following two conditions is satisfied ... 

The reactor models presented in Chapters 4 7 were based on specific flow assumptions, such as the well-mixed reactor and plug flow reactors. Experimental reactors must retain these flow attributes if we wish to use the simple material balances for estimating model parameters. 

Calculate the effect of recycle on the conversion in tubular reactors with plug flow. NONIDEAL FLOW PATTERNS AND POPULATION BALANCE MODELS 655... 

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